If there are multiple serial numbers on a gun, which number should be entered first?

The correct answer is the frame serial number because the frame is considered the "firearm" itself under federal law. In most jurisdictions, the frame or receiver contains the operating components of the gun and is typically the part that is registered and tracked. This is vital for identifying the weapon, as the frame is crucial for the gun's operation and is the main component to which any other parts are connected.

In terms of prioritization, if a firearm has multiple serial numbers associated with various components like the trigger, barrel, or slide, law enforcement agencies and databases prioritize the frame serial number to ensure accurate tracking and registration. This aligns with standards utilized by the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) and various law enforcement protocols for firearms identification.